[.NET Core Uninstall Tool] Hand-off documentation

### What is remaining to do

1. [Windows only] Wrap the single executable with an MSI. As discussed, @wli3 will be working on this.

Relevant code from other codebases:
* https://github.com/dotnet/core-sdk/tree/master/src/redist/targets/packaging/windows/clisdk
* https://github.com/dotnet/core-sdk/blob/master/src/redist/targets/GenerateMSIs.targets

2. Submit the MSI completed in the previous item to the anti-virus check.

3. Approve and merge the PR for the documentation at dotnet/docs#13562.

4. Host the MSI (Windows) and the single executable (macOS) and create a webpage. According to @rowanmiller, the webpage has been done.

### Contact information of original author

In case there is confusion about the codebase, the design of the code structure, etc., I am always happy to help. As I have left Microsoft by the time you read this document, following is my personal contact information:

* Email: panyuchong@gmail.com
* GitHub: @yuchong-pan

Please feel free to contact me regarding this project.